Nano Argovia projects – Effect of cosmic radiation on power semiconductors

In the Nano Argovia project CRONOS, an interdisciplinary team of scientists is studying the effect of cosmic radiation on specific layers in power semiconductors. The researchers want to gain a better understanding of which physical processes can lead to failures in order to apply these insights to the development of power semiconductors offering greater robustness.

Seen here loaded with semiconductor chips for the planned irradiation experiments, the sample holder was developed as part of the Nano Argovia project CRONOS. (Image: FHNW Windisch)

Suitable for high currents and voltages
Fossil fuels are out. Instead, an increasing number of applications are being electrified and supplied with energy from renewable sources. This process calls for semiconductor components that are designed to handle high currents and voltages.

Crucially, the functionality of these modern power semiconductors depends on the reliability and integrity of the “gate oxide layer” — a layer between the gate electrode and the semiconductor substrate. Typically just 50–100 nanometers thick, this layer is required to prevent leakage currents. When used in outdoor applications, such as in electric vehicles, solar installations or wind turbines, the gate oxide layers are exposed to large temperature variations, moisture and even cosmic radiation for a period of many years. Despite these harsh environmental conditions, their properties must not change — and the layers must continue to operate reliably over a long period of time without malfunctioning.

Load test with exposure to radiation
In the Nano Argovia project CRONOS, researchers from the FHNW School of Engineering (Windisch), the ANAXAM technology transfer center and the industrial partner SwissSEM Technologies AG (Lenzburg) are investigating how reliably these nanoscale gate oxide layers operate under controlled exposure to cosmic radiation. To do this, the researchers simulate cosmic radiation by irradiating power semiconductors with protons and neutrons while simultaneously applying a voltage. The team, which is led by Professor Renato Minamisawa and Professor Nicola Schulz (both from the FHNW), then subjects the gate oxide layers to electrical and thermal load testing.Developed and supplied by the industrial partner SwissSEM Technologies, the power semiconductors are insulated-gate bipolar transistors (IGBTs) that can be used in many high-power applications where electric energy needs to be converted into a specific form, for instance in electric vehicles.

By studying the power semiconductors in detail, the researchers hope to gain a better understanding of the physical processes that cause components to fail when cosmic radiation penetrates the gate oxide layers. They then hope to apply this understanding to the development of more-robust power semiconductors.

“For us, the Nano Argovia project CRONOS is an ideal opportunity to work with experts in the field of power semiconductors and material analysis and to benefit from their expertise.”

Dr. Arnost Kopta, CTO SwissSEM Technologies AG

Further information:

Nano Argovia program

SwissSEM GmbH

FHNW School of Engineering